【Basic Knowledge 31】How should heat exchangers be used? Why? (Premiated quiz)
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As the title says. When starting up the heat exchanger, the cold flow should be turned on first, followed by the hot flow; when shutting it down, the process is reversed. This is done to allow the equipment to warm up gradually, preventing it from cracking due to sudden exposure to heat or cold, which could lead to leaks.
Precautions to be taken when the heat exchanger is in operation include: (1) The heat exchanger must undergo pressure testing after being newly installed or after maintenance before it can be put into use. (2) When starting up the heat exchanger, the cold flow should be introduced first, followed by the hot flow; when shutting it down, the hot flow should be stopped first, followed by the cold flow. To prevent leaks or damage caused by uneven thermal expansion and contraction. (3) Fixed-tube-sheet heat exchangers are not allowed to be heated in one direction, and excessive temperature differences are also not permitted on either side of the tubes and shell in floating-type heat exchangers. (4) During startup, the exhaust valve should remain open to allow all air to be expelled, and it should be closed after startup is complete. (5) If hydrocarbons are used, the air in the heat exchanger must be purged with an inert gas before filling it with hydrocarbons to prevent explosions. (6) During shutdown purging, the condensate must be completely drained before introducing steam, and ventilation should be carried out slowly to prevent water hammer. When ventilating one side of the heat exchanger, it is necessary to open the drain valve on the other side to prevent damage due to excessive pressure. When shutting down the heat exchanger, the exhaust valve and the drain valve should be opened to avoid damage to the equipment caused by a vacuum forming as a result of cooling. (7) When using the air cooler, pay attention to ensuring even flow in certain areas to guarantee an effective cooling effect. (8) Regularly pay attention to monitoring to prevent leaks.
A heat exchanger is a device used for heat exchange, reducing the temperature of the hot medium and raising the temperature of the cold medium to meet the requirements of the process medium reaction.
When putting a heat exchanger into use, it should be started by cooling it first and then heating it； Advanced hot materials can cause the various components to expand thermally, while cooler media can cause them to contract rapidly; this temperature difference pressure may lead to leaks in the static seals.
(1) The heat exchanger must undergo pressure testing and pass it before it can be put into use after new installation or after maintenance is completed. (2) When starting up the heat exchanger, the cold flow should be introduced first, followed by the hot flow; when shutting it down, the hot flow should be stopped first, followed by the cold flow. (3) During startup, the cooling water exhaust valve should remain open to allow all air to be expelled, and it should be closed after startup is complete.
1) Heat exchangers must undergo pressure testing and pass it before they can be used after new installation or after maintenance is completed. (2) When starting up the heat exchanger, the cold flow should be introduced first, followed by the hot flow; when shutting it down, the hot flow should be stopped first, followed by the cold flow. (3) During startup, the cooling water exhaust valve should remain open to allow all air to be expelled, and it should be closed after startup is complete.
Precautions to be taken when the heat exchanger is in operation include: (1) The heat exchanger must undergo pressure testing after being newly installed or after maintenance before it can be put into use. (2) When starting up the heat exchanger, the cold flow should be introduced first, followed by the hot flow; when shutting it down, the hot flow should be stopped first, followed by the cold flow. To prevent leaks or damage caused by uneven thermal expansion and contraction. (3) Fixed-tube-sheet heat exchangers are not allowed to be heated in one direction, and excessive temperature differences are also not permitted on either side of the tubes and shell in floating-type heat exchangers. (4) During startup, the exhaust valve should remain open to allow all air to be expelled, and it should be closed after startup is complete. (5) If hydrocarbons are used, the air in the heat exchanger must be purged with an inert gas before filling it with hydrocarbons to prevent explosions. (6) During shutdown purging, the condensate must be completely drained before introducing steam, and ventilation should be carried out slowly to prevent water hammer. When ventilating one side of the heat exchanger, it is necessary to open the drain valve on the other side to prevent damage due to excessive pressure. When shutting down the heat exchanger, the exhaust valve and the drain valve should be opened to avoid damage to the equipment caused by a vacuum forming as a result of cooling. (7) When using the air cooler, pay attention to ensuring even flow in certain areas to guarantee an effective cooling effect. (8) Regularly pay attention to monitoring to prevent leaks.
Start with the cold flow first, then the hot flow; when stopping, do the opposite, to prevent the heat exchanger from being subjected to sudden changes in temperature and thus cracking